The president reiterates that those responsible will be caught and brought to justice.
President Obama on Wednesday vowed that authorities will do all that they can to catch the people behind the Boston Marathon bombings. So far little is known beyond the number of bombs detonated and the damage they caused.
"We know that two explosions gravely wounded dozens of Americans and took the lives of others, including an eight-year-old boy. This was a heinous and cowardly act and given what we now know about what took place, the FBI is now investigating it as an act of terrorism," Obama said in remarks delivered from the White House briefing room Tuesday morning.
He added that what's not known is who carried out the attack or why, how many people were involved or whether it was carried out by a terrorist group or a "malevolent individual," but whomever is responsible, he said, will be found and brought to justice.
"The American people refused to be terrorized. Because what the world saw yesterday in the aftermath of the explosions were stories of heroism and kindness and generosity and love," he said, praising people who raced to local hospitals to give blood or stayed behind to help the injured, first responders and others.
"So if you want to know who we are, what America is, how we respond to evil, that's it: selflessly, compassionately, not afraid," he said.
Later in the day, FBI agent Richard DesLauriers said the bombs may have been made using metal pressure cookers filled with such materials as nails and ball bearings and then hidden in a black nylon bag or backpack. Similar explosives were used in Afghanistan, India, Pakistan and Nepal, according to a 2010 FBI/Homeland Security Department report, and household materials also were recommended in the chapter of an Al-qaeda publication titled "Make a Bomb in the Kitchen of Your Mom."
While no closer to finding the cultprits or evidence that the attacks were part of a wider plot, DesLauriers said "the range of suspects and motives remains wide open."
"We will go to the ends of the Earth to identify the subject or subjects who are responsible for this despicable crime, and we will do everything we can to bring them to justice," DesLauriers said.
Obama will travel to Boston on Thursday to participate in an interfaith service for the bombing victims.
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(Photo: Mark Wilson/Getty Images)